Change of blood lactate metabolism accompanies both disease related states of stress/anxiety and normal states of rest/relaxation in man. We plan to investigate the physiologic basis of decreased blood lactate that occurs during acute rest/relaxation behavior with a view toward adding to our understanding of the mechanisms and importance of change of lactate metabolism in states of health and disease. In particular, we plan to confirm preliminary findings that rest states can inhibit rate of lactate generation by formed blood elements and to establish the possible existence of plasma inhibitory factor(s) induced by these forms of behavior. For this purpose, groups of 15 subjects will be studied during common stylized relaxation procedures (the practices known as "transcendental meditation" (TM) and the "relaxation response" (RR) and during normal eyes closed rest and sleep. Subjects will be studied on a separate control reading occasion. Arterial blood samples will be drawn every 20 minutes and rate of lactate generation at 37 degrees and 25 degrees measured and compared between practice and reading occasions. Plasma from samples in which decreased lactate generation rate has been identified will be added to control blood elements for confirmation of possible plasma inhibitory factor.